The invention relates to a centrifugal pump unit and more particularly, a centrifugal pump unit comprising an electromagmetic flow switch and a two-armed, pivotally mounted lever.
Centrifugal pump units are used today for increasing the pressure, as so-called booster pumps. In particular, where the central water supply does not constantly have an adequately high operating pressure it is usual to install storage tanks in the roof, wherein then the water is filled from the central water supply up to a certain degree of filling into the storage tank and from here when required flows to the water tapping location in the households located thereunder. By way of this, water may also be tapped when in the central supply conduit the delivery pressure falls or the supply is stopped. Since the static pressure of account of the height difference between the storage tank and the tapping location is mostly only very slight, when electrical or gas-driven water heaters or comparable apparatus which demand a minimum water through-flow are used, it is then necessary to use such booster pumps. Booster pumps are typically used for pressure increases of 0.6 to 0.8 bar with a delivery flow of 0.5 to 1 m.sup.3 /h.
Since the pressure increase is only required when water is removed, thus when the water heater or a similar apparatus is operated, these pumps are equipped with a flow switch which controls the electric motor of the centrifugal pump unit. When a tap valve is opened at a tapping location and water begins to flow on account of the low present static pressure, this flow switch is stimulated which thereupon switches on the motor of the centrifugal pump unit in order in this manner to produce the desired pressure increase.
Such centrifugal pump units belong to the state of the art. A known such unit is specially designed for this application purpose and comprises a terminal box which covers the motor housing up to the pump housing and here comprises an electromagnetic switch device which is in active connection with a two-armed, pivotably mounted lever arranged in this region in the flow path. This lever with one arm projects in the flow path and on the other arm carries a magnet which controls the switch device in the form of a reed contact.
The disadvantage with this type of construction is the fact that almost all components are usable exclusively for this pump type, in particular that the terminal box with regard to design is adapted to this special centrifugal pump unit.